Balloon dilatation catheters are used in medical procedures in which a body vessel is dilated. One such procedure is angioplasty, in which a stenosed, narrowed blood vessel is widened using an inflatable balloon catheter. Balloon catheters are also used for stent delivery. The balloon catheter typically includes an elongate, flexible shaft having an inflatable balloon disposed near the catheter distal end. The shaft commonly includes an inflation lumen within. The inflation lumen is in fluid communication with the balloon such that balloon inflation is accomplished by injecting fluid under pressure into the inflation lumen. The catheter can also have a guide wire lumen either extending the length of the shaft in "over the wire" catheters or extending only the length of the balloon or the length of the balloon and part of the shaft in "single operator exchange" catheters. The catheters are long enough to extend from an insertion point near the groin or arm to the coronary arteries.
During treatment, the inflation lumen is filled with inflation fluid under pressure, causing balloon expansion within the narrowed region to be dilated. Prior to treatment, the catheter must be prepared for use. Preparation includes preloading the inflation lumen and balloon with inflation fluid. Preparations also include purging the catheter inflation lumen and balloon of air. Balloon catheters have commonly had a single orifice for both injecting inflation fluid into the catheter and releasing air from the catheter. Specifically, the inflation lumen proximal port is typically the only orifice through which inflation fluid passes.
Inflation fluid can be injected into the inflation lumen proximal port while the catheter is held vertically such that the balloon is much lower than the proximal port. Alternately, inflation fluid can be drawn in by pulling a vacuum from the distal end of the catheter. Some air bubbles rise through the sinking inflation fluid, the inflation fluid partially adhering to tube walls due to surface tension. It would be more desirable to have both an inflation fluid inlet and outlet orifice, allowing for inflation fluid entry through one orifice and air and fluid exit through the other orifice.
Bromander, in U.S. Pat. No. 5,100,385, proposes placing a one-way valve between the guide wire lumen and inflation lumen. Bromander discusses using the proximal guide wire port for entry of inflation fluid, and using the proximal inflation lumen port for exit of inflation fluid. In the Bromander design, bleeding the catheter while having inflation injection equipment attached can be difficult as the inflation fluid entry and bleed ports are one in the same. The Bromander design also positions the one-way valve within the balloon. This is less than optimal, as the distally disposed balloon preferably has a small profile and locating the valve within the balloon can increase this profile. The balloon, during preparation, is preferably tightly wrapped and constrained within a balloon protector, leaving little room for movement of the one-way valve mechanism.
What would be desirable is an improved balloon catheter capable of being rapidly purged of air and filled with inflation fluid prior to use. An improved method for rapidly purging and filling a balloon catheter with inflation fluid would be desirable.